This invention generally relates to water pumps and in particular to a water pump used in appliances.
Dishwashers and washing machines use water pumps to move liquid through and out of the appliance in a series of wash, rinse, and drain cycles. Such pumps include a rigid housing, a rigid cover, and an impeller which slip fits onto a drive shaft or motor shaft. The pump also includes a mechanical face seal, consisting of a seal head assembly and a seal seat, for preventing liquid leakage between the fixed, rigid housing and the rotating impeller. Also, a two-piece thrust bearing, with one half mounted in the impeller for running against the other half, that is mounted in the rigid cover.
The thrust bearing resists the axial force of the mechanical face seal and also establishes the axial running clearances of the impeller with both the rigid housing and the rigid cover, as well as determining the axial operating height of the mechanical face seal assembly. However, this system is complex and costly and subject to premature failure due to wear-out of the thrust bearing by abrasive laden liquid. Such wear-out also destroys the running clearances and operating height. This, in turn, can cause the impeller to prematurely wear away or even melt through the rigid cover, and can also cause the mechanical face seal to leak excessively. Thus, there is a need for a simpler, more cost effective and reliable water pump for appliances that is also easy to assemble and service.